The present invention relates to a joint structure and a joining method by which a metal component and a resin component are joined together with seal material in between. For example, the present invention relates to a joint structure and a joining method by which a metallic oil control valve of an engine and a synthetic resin cylinder head cover that incorporates the oil control valve are joined together.
In a conventional art, such joint of a metal component and a resin component is carried out, for example, in the following manner. First, a recess formed in the metal component is filled with a seal material in a liquid form. Resin material is then supplied onto the metal component and the resin component and the metal component are molded as an integral body. Simultaneously, the seal material in the liquid form is cured. In this manner, the seal material seals the joint portion between the metal component and the resin component.
Japanese Laid-Open Patent Publication No. 2006-339403 discloses one such joint structure between a metal component and a resin component. The joint structure is employed in manufacturing a case that accommodates an electric component such as an electronic control circuit. Specifically, seal material in a liquid form is caused to fill a recess formed in the metal component and cured. Then, resin material in a molten state is provided on the metal component and thus the resin component and the metal component are molded as an integral body.
However, in the joint structure of the former conventional art, when the resin material is supplied onto the metal component with the recess filled with the seal material in the liquid form, pressure produced by the flow of the resin material may cause the seal material to flow out of the recess. As a result, desirable sealing performance may not be obtained in the joint portion between the metal component and the resin component.
To solve this problem, seal material in a liquid form having such a viscosity that the seal material does not flow out of the recess may be employed. However, the seal material in the liquid form with this level of viscosity lowers the work efficiency of filling the recess of the metal component with the seal material. Further, air may easily be caught between the seal material and the metal component in the recess. In this case, the air may lower the sealing performance.
In the joint structure of the aforementioned publication, the seal material may flow out of the recess, as in the case of the former conventional art, if the resin material in the molten state is supplied onto the metal material before the seal material is cured. However, after the seal material is sufficiently cured, the resin material flows between the seal material and the metal component when the resin material in the molten state is provided. Air is caught in corners of the recess at a position downstream in the flow direction of the resin material. This can lower the sealing performance.